The present invention relates generally to a machine for making multiple-ply paper products, such as cardboard and the like.
Machines for making multiple-ply paper products, such as cardboard or the like, are already known. Generally speaking, they have heretofore used a screen or forming wire on which one layer or ply of the paper product was directly formed. Since this had to cooperate with other wires for other plys, and considering the relatively large number of plys which is often required in making cardboard, the carrier screen or forming wire often had to be very long. Such very long forming wires, however, are extremely expensive and highly susceptible to damage. Moreover, when a new forming wire of such great length is to be installed in the machine, a very substantial amount of time is required for its installation, meaning of course that the utilization of such screens is highly labor-intensive. Moreover, they are evidently capital-intensive since a relative large outlay of capital is required to obtain such screens.
For these reasons the prior art has already proposed to provide two forming wires, one behind the other, each of which is associated with several upper screens or forming wires. However, in these constructions, also, the main forming wires can be replaced only if all of the components located within the loop formed by the endless forming wire can be shifted out of the loop by appropriately mounting them, which is evidently highly expensive, or if other difficult, cumbersome and space-consuming expedients are utilized.
Since this also was not satisfactory in terms of the desired ease of replacing the main forming wire, another approach suggested by the prior art has been to insert the strip-shaped forming wire into the machine, train it about the various rollers and other components with which it cooperates, and then weld its ends together to form an endless belt. This approach facilitates the installation of the forming wire, but has the disadvantage that the welded seam which must be produced frequently is not durable enough to last for the required period of time. Moreover, it is not usually possible to so construct the seam that it will not leave marks on the cardboard or other paper product being produced, which is clearly not permissible.